Sum Data Using Dates and Additional Criteria

I'm trying to sum hours for certain discipline between periods of time that are about a month apart. I have figured out how to sum all the hours for all the disciplines for that time period but have failed at sum the hours for each discipline. What I've got so far is:

=SUMIF(bbb,"<="&DATE(2004,10,29),ccc)-SUMIF(bbb,"<"&DATE(2004,9,25),ccc)

aaa=range of Disciplines 1-28, bbb=range of dates, ccc=range of hours.
(each of these represent a range that are in a single column)

What do I need to add or change to this function in order for it to only sum a specific discipline between the dates, not all of the disciplines between the dates? For example if I wanted to sum only the hours of discipline 1 between
9/25/2004 & 10/29/2004. Discipline 1 is in the range aaa.

I would appreciate if someone could point me in the right direction on this.

Yes I think it is an array formula. Ill look over your links and see if I can find anything that helps, thanks.

I tried it and it gave me #NUM!.Is there anything in my data formatting that would cause this problem?

Worked like a charm. TYVM